1. Field of the Invention
The invention relates generally to the field of photography, and in particular to film cartridges. More specifically, the invention relates to an alternative airtight seal and use indicator for a film cartridge.
2. Description of the Prior Art
It is known as disclosed in commonly assigned U.S. Pat. No. 4,647,170, issued Mar. 3, 1987, to provide a conventional 35 mm film cartridge with a compressible plug which can be pushed inwardly within the coaxial cavity at one end portion of the hub of the film spool to indicate the film cartridge has been used. The end portion of the hub extends through a coaxial opening in the cartridge housing to the outside of the housing.
Also, U.S. Pat. No. 5,032,862, issued Jul. 16, 1991, discloses a similar 35 mm cartridge in which the cavity in the end portion of the hub is covered with a disk-shaped label that can be pierced to indicate the film cartridge has been used. A problem with the label is that it may leave debris when pierced.